net/smc/smc_tx.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Shared Memory Communications over RDMA (SMC-R) and RoCE
  *
  * Manage send buffer.
  * Producer:
  * Copy user space data into send buffer, if send buffer space available.
  * Consumer:
  * Trigger RDMA write into RMBE of peer and send CDC, if RMBE space available.
  *
  * Copyright IBM Corp. 2016
  *
  * Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
  */

 #include <linux/net.h>
 #include <linux/rcupdate.h>
 #include <linux/workqueue.h>
 #include <linux/sched/signal.h>

 #include <net/sock.h>
 #include <net/tcp.h>

 #include "smc.h"
 #include "smc_wr.h"
 #include "smc_cdc.h"
 #include "smc_close.h"
 #include "smc_ism.h"
 #include "smc_tx.h"

 #define SMC_TX_WORK_DELAY	0
 #define SMC_TX_CORK_DELAY	(HZ >> 2)	/* 250 ms */

 /***************************** sndbuf producer *******************************/

 /* callback implementation for sk.sk_write_space()
  * to wakeup sndbuf producers that blocked with smc_tx_wait().
  * called under sk_socket lock.
  */
 static void smc_tx_write_space(struct sock *sk)
 {
 	struct socket *sock = sk->sk_socket;
 	struct smc_sock *smc = smc_sk(sk);
 	struct socket_wq *wq;

 	/* similar to sk_stream_write_space */
 	if (atomic_read(&smc->conn.sndbuf_space) && sock) {
 		clear_bit(SOCK_NOSPACE, &sock->flags);
 		rcu_read_lock();
 		wq = rcu_dereference(sk->sk_wq);
 		if (skwq_has_sleeper(wq))
 			wake_up_interruptible_poll(&wq->wait,
 						   EPOLLOUT | EPOLLWRNORM |
 						   EPOLLWRBAND);
 		if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
 			sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
 		rcu_read_unlock();
 	}
 }

 /* Wakeup sndbuf producers that blocked with smc_tx_wait().
  * Cf. tcp_data_snd_check()=>tcp_check_space()=>tcp_new_space().
  */
 void smc_tx_sndbuf_nonfull(struct smc_sock *smc)
 {
 	if (smc->sk.sk_socket &&
 	    test_bit(SOCK_NOSPACE, &smc->sk.sk_socket->flags))
 		smc->sk.sk_write_space(&smc->sk);
 }

 /* blocks sndbuf producer until at least one byte of free space available
  * or urgent Byte was consumed
  */
 static int smc_tx_wait(struct smc_sock *smc, int flags)
 {
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 	struct smc_connection *conn = &smc->conn;
 	struct sock *sk = &smc->sk;
 	long timeo;
 	int rc = 0;

 	/* similar to sk_stream_wait_memory */
 	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
 		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 		if (sk->sk_err ||
 		    (sk->sk_shutdown & SEND_SHUTDOWN) ||
 		    conn->killed ||
 		    conn->local_tx_ctrl.conn_state_flags.peer_done_writing) {
 			rc = -EPIPE;
 			break;
 		}
 		if (smc_cdc_rxed_any_close(conn)) {
 			rc = -ECONNRESET;
 			break;
 		}
 		if (!timeo) {
 			/* ensure EPOLLOUT is subsequently generated */
 			set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 			rc = -EAGAIN;
 			break;
 		}
 		if (signal_pending(current)) {
 			rc = sock_intr_errno(timeo);
 			break;
 		}
 		sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 		if (atomic_read(&conn->sndbuf_space) && !conn->urg_tx_pend)
 			break; /* at least 1 byte of free & no urgent data */
 		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 		sk_wait_event(sk, &timeo,
 			      sk->sk_err ||
 			      (sk->sk_shutdown & SEND_SHUTDOWN) ||
 			      smc_cdc_rxed_any_close(conn) ||
 			      (atomic_read(&conn->sndbuf_space) &&
 			       !conn->urg_tx_pend),
 			      &wait);
 	}
 	remove_wait_queue(sk_sleep(sk), &wait);
 	return rc;
 }

 static bool smc_tx_is_corked(struct smc_sock *smc)
 {
 	struct tcp_sock *tp = tcp_sk(smc->clcsock->sk);

 	return (tp->nonagle & TCP_NAGLE_CORK) ? true : false;
 }

 /* sndbuf producer: main API called by socket layer.
  * called under sock lock.
  */
 int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
 {
 	size_t copylen, send_done = 0, send_remaining = len;
 	size_t chunk_len, chunk_off, chunk_len_sum;
 	struct smc_connection *conn = &smc->conn;
 	union smc_host_cursor prep;
 	struct sock *sk = &smc->sk;
 	char *sndbuf_base;
 	int tx_cnt_prep;
 	int writespace;
 	int rc, chunk;

 	/* This should be in poll */
 	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);

 	if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
 		rc = -EPIPE;
 		goto out_err;
 	}

 	while (msg_data_left(msg)) {
 		if (sk->sk_state == SMC_INIT)
 			return -ENOTCONN;
 		if (smc->sk.sk_shutdown & SEND_SHUTDOWN ||
 		    (smc->sk.sk_err == ECONNABORTED) ||
 		    conn->killed)
 			return -EPIPE;
 		if (smc_cdc_rxed_any_close(conn))
 			return send_done ?: -ECONNRESET;

 		if (msg->msg_flags & MSG_OOB)
 			conn->local_tx_ctrl.prod_flags.urg_data_pending = 1;

 		if (!atomic_read(&conn->sndbuf_space) || conn->urg_tx_pend) {
 			if (send_done)
 				return send_done;
 			rc = smc_tx_wait(smc, msg->msg_flags);
 			if (rc)
 				goto out_err;
 			continue;
 		}

 		/* initialize variables for 1st iteration of subsequent loop */
 		/* could be just 1 byte, even after smc_tx_wait above */
 		writespace = atomic_read(&conn->sndbuf_space);
 		/* not more than what user space asked for */
 		copylen = min_t(size_t, send_remaining, writespace);
 		/* determine start of sndbuf */
 		sndbuf_base = conn->sndbuf_desc->cpu_addr;
 		smc_curs_copy(&prep, &conn->tx_curs_prep, conn);
 		tx_cnt_prep = prep.count;
 		/* determine chunks where to write into sndbuf */
 		/* either unwrapped case, or 1st chunk of wrapped case */
 		chunk_len = min_t(size_t, copylen, conn->sndbuf_desc->len -
 				  tx_cnt_prep);
 		chunk_len_sum = chunk_len;
 		chunk_off = tx_cnt_prep;
 		smc_sndbuf_sync_sg_for_cpu(conn);
 		for (chunk = 0; chunk < 2; chunk++) {
 			rc = memcpy_from_msg(sndbuf_base + chunk_off,
 					     msg, chunk_len);
 			if (rc) {
 				smc_sndbuf_sync_sg_for_device(conn);
 				if (send_done)
 					return send_done;
 				goto out_err;
 			}
 			send_done += chunk_len;
 			send_remaining -= chunk_len;

 			if (chunk_len_sum == copylen)
 				break; /* either on 1st or 2nd iteration */
 			/* prepare next (== 2nd) iteration */
 			chunk_len = copylen - chunk_len; /* remainder */
 			chunk_len_sum += chunk_len;
 			chunk_off = 0; /* modulo offset in send ring buffer */
 		}
 		smc_sndbuf_sync_sg_for_device(conn);
 		/* update cursors */
 		smc_curs_add(conn->sndbuf_desc->len, &prep, copylen);
 		smc_curs_copy(&conn->tx_curs_prep, &prep, conn);
 		/* increased in send tasklet smc_cdc_tx_handler() */
 		smp_mb__before_atomic();
 		atomic_sub(copylen, &conn->sndbuf_space);
 		/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
 		smp_mb__after_atomic();
 		/* since we just produced more new data into sndbuf,
 		 * trigger sndbuf consumer: RDMA write into peer RMBE and CDC
 		 */
 		if ((msg->msg_flags & MSG_OOB) && !send_remaining)
 			conn->urg_tx_pend = true;
 		if ((msg->msg_flags & MSG_MORE || smc_tx_is_corked(smc)) &&
 		    (atomic_read(&conn->sndbuf_space) >
 						(conn->sndbuf_desc->len >> 1)))
 			/* for a corked socket defer the RDMA writes if there
 			 * is still sufficient sndbuf_space available
 			 */
 			queue_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
 					   SMC_TX_CORK_DELAY);
 		else
 			smc_tx_sndbuf_nonempty(conn);
 	} /* while (msg_data_left(msg)) */

 	return send_done;

 out_err:
 	rc = sk_stream_error(sk, msg->msg_flags, rc);
 	/* make sure we wake any epoll edge trigger waiter */
 	if (unlikely(rc == -EAGAIN))
 		sk->sk_write_space(sk);
 	return rc;
 }

 /***************************** sndbuf consumer *******************************/

 /* sndbuf consumer: actual data transfer of one target chunk with ISM write */
 int smcd_tx_ism_write(struct smc_connection *conn, void *data, size_t len,
 		      u32 offset, int signal)
 {
 	struct smc_ism_position pos;
 	int rc;

 	memset(&pos, 0, sizeof(pos));
 	pos.token = conn->peer_token;
 	pos.index = conn->peer_rmbe_idx;
 	pos.offset = conn->tx_off + offset;
 	pos.signal = signal;
 	rc = smc_ism_write(conn->lgr->smcd, &pos, data, len);
 	if (rc)
 		conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
 	return rc;
 }

 /* sndbuf consumer: actual data transfer of one target chunk with RDMA write */
 static int smc_tx_rdma_write(struct smc_connection *conn, int peer_rmbe_offset,
 			     int num_sges, struct ib_rdma_wr *rdma_wr)
 {
 	struct smc_link_group *lgr = conn->lgr;
 	struct smc_link *link = conn->lnk;
 	int rc;

 	rdma_wr->wr.wr_id = smc_wr_tx_get_next_wr_id(link);
 	rdma_wr->wr.num_sge = num_sges;
 	rdma_wr->remote_addr =
 		lgr->rtokens[conn->rtoken_idx][link->link_idx].dma_addr +
 		/* RMBE within RMB */
 		conn->tx_off +
 		/* offset within RMBE */
 		peer_rmbe_offset;
 	rdma_wr->rkey = lgr->rtokens[conn->rtoken_idx][link->link_idx].rkey;
 	rc = ib_post_send(link->roce_qp, &rdma_wr->wr, NULL);
 	if (rc)
 		smcr_link_down_cond_sched(link);
 	return rc;
 }

 /* sndbuf consumer */
 static inline void smc_tx_advance_cursors(struct smc_connection *conn,
 					  union smc_host_cursor *prod,
 					  union smc_host_cursor *sent,
 					  size_t len)
 {
 	smc_curs_add(conn->peer_rmbe_size, prod, len);
 	/* increased in recv tasklet smc_cdc_msg_rcv() */
 	smp_mb__before_atomic();
 	/* data in flight reduces usable snd_wnd */
 	atomic_sub(len, &conn->peer_rmbe_space);
 	/* guarantee 0 <= peer_rmbe_space <= peer_rmbe_size */
 	smp_mb__after_atomic();
 	smc_curs_add(conn->sndbuf_desc->len, sent, len);
 }

 /* SMC-R helper for smc_tx_rdma_writes() */
 static int smcr_tx_rdma_writes(struct smc_connection *conn, size_t len,
 			       size_t src_off, size_t src_len,
 			       size_t dst_off, size_t dst_len,
 			       struct smc_rdma_wr *wr_rdma_buf)
 {
 	struct smc_link *link = conn->lnk;

 	dma_addr_t dma_addr =
 		sg_dma_address(conn->sndbuf_desc->sgt[link->link_idx].sgl);
 	int src_len_sum = src_len, dst_len_sum = dst_len;
 	int sent_count = src_off;
 	int srcchunk, dstchunk;
 	int num_sges;
 	int rc;

 	for (dstchunk = 0; dstchunk < 2; dstchunk++) {
 		struct ib_sge *sge =
 			wr_rdma_buf->wr_tx_rdma[dstchunk].wr.sg_list;

 		num_sges = 0;
 		for (srcchunk = 0; srcchunk < 2; srcchunk++) {
 			sge[srcchunk].addr = dma_addr + src_off;
 			sge[srcchunk].length = src_len;
 			num_sges++;

 			src_off += src_len;
 			if (src_off >= conn->sndbuf_desc->len)
 				src_off -= conn->sndbuf_desc->len;
 						/* modulo in send ring */
 			if (src_len_sum == dst_len)
 				break; /* either on 1st or 2nd iteration */
 			/* prepare next (== 2nd) iteration */
 			src_len = dst_len - src_len; /* remainder */
 			src_len_sum += src_len;
 		}
 		rc = smc_tx_rdma_write(conn, dst_off, num_sges,
 				       &wr_rdma_buf->wr_tx_rdma[dstchunk]);
 		if (rc)
 			return rc;
 		if (dst_len_sum == len)
 			break; /* either on 1st or 2nd iteration */
 		/* prepare next (== 2nd) iteration */
 		dst_off = 0; /* modulo offset in RMBE ring buffer */
 		dst_len = len - dst_len; /* remainder */
 		dst_len_sum += dst_len;
 		src_len = min_t(int, dst_len, conn->sndbuf_desc->len -
 				sent_count);
 		src_len_sum = src_len;
 	}
 	return 0;
 }

 /* SMC-D helper for smc_tx_rdma_writes() */
 static int smcd_tx_rdma_writes(struct smc_connection *conn, size_t len,
 			       size_t src_off, size_t src_len,
 			       size_t dst_off, size_t dst_len)
 {
 	int src_len_sum = src_len, dst_len_sum = dst_len;
 	int srcchunk, dstchunk;
 	int rc;

 	for (dstchunk = 0; dstchunk < 2; dstchunk++) {
 		for (srcchunk = 0; srcchunk < 2; srcchunk++) {
 			void *data = conn->sndbuf_desc->cpu_addr + src_off;

 			rc = smcd_tx_ism_write(conn, data, src_len, dst_off +
 					       sizeof(struct smcd_cdc_msg), 0);
 			if (rc)
 				return rc;
 			dst_off += src_len;
 			src_off += src_len;
 			if (src_off >= conn->sndbuf_desc->len)
 				src_off -= conn->sndbuf_desc->len;
 						/* modulo in send ring */
 			if (src_len_sum == dst_len)
 				break; /* either on 1st or 2nd iteration */
 			/* prepare next (== 2nd) iteration */
 			src_len = dst_len - src_len; /* remainder */
 			src_len_sum += src_len;
 		}
 		if (dst_len_sum == len)
 			break; /* either on 1st or 2nd iteration */
 		/* prepare next (== 2nd) iteration */
 		dst_off = 0; /* modulo offset in RMBE ring buffer */
 		dst_len = len - dst_len; /* remainder */
 		dst_len_sum += dst_len;
 		src_len = min_t(int, dst_len, conn->sndbuf_desc->len - src_off);
 		src_len_sum = src_len;
 	}
 	return 0;
 }

 /* sndbuf consumer: prepare all necessary (src&dst) chunks of data transmit;
  * usable snd_wnd as max transmit
  */
 static int smc_tx_rdma_writes(struct smc_connection *conn,
 			      struct smc_rdma_wr *wr_rdma_buf)
 {
 	size_t len, src_len, dst_off, dst_len; /* current chunk values */
 	union smc_host_cursor sent, prep, prod, cons;
 	struct smc_cdc_producer_flags *pflags;
 	int to_send, rmbespace;
 	int rc;

 	/* source: sndbuf */
 	smc_curs_copy(&sent, &conn->tx_curs_sent, conn);
 	smc_curs_copy(&prep, &conn->tx_curs_prep, conn);
 	/* cf. wmem_alloc - (snd_max - snd_una) */
 	to_send = smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep);
 	if (to_send <= 0)
 		return 0;

 	/* destination: RMBE */
 	/* cf. snd_wnd */
 	rmbespace = atomic_read(&conn->peer_rmbe_space);
 	if (rmbespace <= 0)
 		return 0;
 	smc_curs_copy(&prod, &conn->local_tx_ctrl.prod, conn);
 	smc_curs_copy(&cons, &conn->local_rx_ctrl.cons, conn);

 	/* if usable snd_wnd closes ask peer to advertise once it opens again */
 	pflags = &conn->local_tx_ctrl.prod_flags;
 	pflags->write_blocked = (to_send >= rmbespace);
 	/* cf. usable snd_wnd */
 	len = min(to_send, rmbespace);

 	/* initialize variables for first iteration of subsequent nested loop */
 	dst_off = prod.count;
 	if (prod.wrap == cons.wrap) {
 		/* the filled destination area is unwrapped,
 		 * hence the available free destination space is wrapped
 		 * and we need 2 destination chunks of sum len; start with 1st
 		 * which is limited by what's available in sndbuf
 		 */
 		dst_len = min_t(size_t,
 				conn->peer_rmbe_size - prod.count, len);
 	} else {
 		/* the filled destination area is wrapped,
 		 * hence the available free destination space is unwrapped
 		 * and we need a single destination chunk of entire len
 		 */
 		dst_len = len;
 	}
 	/* dst_len determines the maximum src_len */
 	if (sent.count + dst_len <= conn->sndbuf_desc->len) {
 		/* unwrapped src case: single chunk of entire dst_len */
 		src_len = dst_len;
 	} else {
 		/* wrapped src case: 2 chunks of sum dst_len; start with 1st: */
 		src_len = conn->sndbuf_desc->len - sent.count;
 	}

 	if (conn->lgr->is_smcd)
 		rc = smcd_tx_rdma_writes(conn, len, sent.count, src_len,
 					 dst_off, dst_len);
 	else
 		rc = smcr_tx_rdma_writes(conn, len, sent.count, src_len,
 					 dst_off, dst_len, wr_rdma_buf);
 	if (rc)
 		return rc;

 	if (conn->urg_tx_pend && len == to_send)
 		pflags->urg_data_present = 1;
 	smc_tx_advance_cursors(conn, &prod, &sent, len);
 	/* update connection's cursors with advanced local cursors */
 	smc_curs_copy(&conn->local_tx_ctrl.prod, &prod, conn);
 							/* dst: peer RMBE */
 	smc_curs_copy(&conn->tx_curs_sent, &sent, conn);/* src: local sndbuf */

 	return 0;
 }

 /* Wakeup sndbuf consumers from any context (IRQ or process)
  * since there is more data to transmit; usable snd_wnd as max transmit
  */
 static int smcr_tx_sndbuf_nonempty(struct smc_connection *conn)
 {
 	struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
 	struct smc_link *link = conn->lnk;
 	struct smc_rdma_wr *wr_rdma_buf;
 	struct smc_cdc_tx_pend *pend;
 	struct smc_wr_buf *wr_buf;
 	int rc;

 	if (!link || !smc_wr_tx_link_hold(link))
 		return -ENOLINK;
 	rc = smc_cdc_get_free_slot(conn, link, &wr_buf, &wr_rdma_buf, &pend);
 	if (rc < 0) {
 		smc_wr_tx_link_put(link);
 		if (rc == -EBUSY) {
 			struct smc_sock *smc =
 				container_of(conn, struct smc_sock, conn);

 			if (smc->sk.sk_err == ECONNABORTED)
 				return sock_error(&smc->sk);
 			if (conn->killed)
 				return -EPIPE;
 			rc = 0;
 			mod_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
 					 SMC_TX_WORK_DELAY);
 		}
 		return rc;
 	}

 	spin_lock_bh(&conn->send_lock);
 	if (link != conn->lnk) {
 		/* link of connection changed, tx_work will restart */
 		smc_wr_tx_put_slot(link,
 				   (struct smc_wr_tx_pend_priv *)pend);
 		rc = -ENOLINK;
 		goto out_unlock;
 	}
 	if (!pflags->urg_data_present) {
 		rc = smc_tx_rdma_writes(conn, wr_rdma_buf);
 		if (rc) {
 			smc_wr_tx_put_slot(link,
 					   (struct smc_wr_tx_pend_priv *)pend);
 			goto out_unlock;
 		}
 	}

 	rc = smc_cdc_msg_send(conn, wr_buf, pend);
 	if (!rc && pflags->urg_data_present) {
 		pflags->urg_data_pending = 0;
 		pflags->urg_data_present = 0;
 	}

 out_unlock:
 	spin_unlock_bh(&conn->send_lock);
 	smc_wr_tx_link_put(link);
 	return rc;
 }

 static int smcd_tx_sndbuf_nonempty(struct smc_connection *conn)
 {
 	struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
 	int rc = 0;

 	spin_lock_bh(&conn->send_lock);
 	if (!pflags->urg_data_present)
 		rc = smc_tx_rdma_writes(conn, NULL);
 	if (!rc)
 		rc = smcd_cdc_msg_send(conn);

 	if (!rc && pflags->urg_data_present) {
 		pflags->urg_data_pending = 0;
 		pflags->urg_data_present = 0;
 	}
 	spin_unlock_bh(&conn->send_lock);
 	return rc;
 }

 int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
 {
 	int rc;

 	if (conn->killed ||
 	    conn->local_rx_ctrl.conn_state_flags.peer_conn_abort)
 		return -EPIPE;	/* connection being aborted */
 	if (conn->lgr->is_smcd)
 		rc = smcd_tx_sndbuf_nonempty(conn);
 	else
 		rc = smcr_tx_sndbuf_nonempty(conn);

 	if (!rc) {
 		/* trigger socket release if connection is closing */
 		struct smc_sock *smc = container_of(conn, struct smc_sock,
 						    conn);
 		smc_close_wake_tx_prepared(smc);
 	}
 	return rc;
 }

 /* Wakeup sndbuf consumers from process context
  * since there is more data to transmit
  */
 void smc_tx_work(struct work_struct *work)
 {
 	struct smc_connection *conn = container_of(to_delayed_work(work),
 						   struct smc_connection,
 						   tx_work);
 	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
 	int rc;

 	lock_sock(&smc->sk);
 	if (smc->sk.sk_err)
 		goto out;

 	rc = smc_tx_sndbuf_nonempty(conn);
 	if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked &&
 	    !atomic_read(&conn->bytes_to_rcv))
 		conn->local_rx_ctrl.prod_flags.write_blocked = 0;

 out:
 	release_sock(&smc->sk);
 }

 void smc_tx_consumer_update(struct smc_connection *conn, bool force)
 {
 	union smc_host_cursor cfed, cons, prod;
 	int sender_free = conn->rmb_desc->len;
 	int to_confirm;

 	smc_curs_copy(&cons, &conn->local_tx_ctrl.cons, conn);
 	smc_curs_copy(&cfed, &conn->rx_curs_confirmed, conn);
 	to_confirm = smc_curs_diff(conn->rmb_desc->len, &cfed, &cons);
 	if (to_confirm > conn->rmbe_update_limit) {
 		smc_curs_copy(&prod, &conn->local_rx_ctrl.prod, conn);
 		sender_free = conn->rmb_desc->len -
 			      smc_curs_diff_large(conn->rmb_desc->len,
 						  &cfed, &prod);
 	}

 	if (conn->local_rx_ctrl.prod_flags.cons_curs_upd_req ||
 	    force ||
 	    ((to_confirm > conn->rmbe_update_limit) &&
 	     ((sender_free <= (conn->rmb_desc->len / 2)) ||
 	      conn->local_rx_ctrl.prod_flags.write_blocked))) {
 		if (conn->killed ||
 		    conn->local_rx_ctrl.conn_state_flags.peer_conn_abort)
 			return;
 		if ((smc_cdc_get_slot_and_msg_send(conn) < 0) &&
 		    !conn->killed) {
 			queue_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
 					   SMC_TX_WORK_DELAY);
 			return;
 		}
 	}
 	if (conn->local_rx_ctrl.prod_flags.write_blocked &&
 	    !atomic_read(&conn->bytes_to_rcv))
 		conn->local_rx_ctrl.prod_flags.write_blocked = 0;
 }

 /***************************** send initialize *******************************/

 /* Initialize send properties on connection establishment. NB: not __init! */
 void smc_tx_init(struct smc_sock *smc)
 {
 	smc->sk.sk_write_space = smc_tx_write_space;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Shared Memory Communications over RDMA (SMC-R) and RoCE
	*
	* Manage send buffer.
	* Producer:
	* Copy user space data into send buffer, if send buffer space available.
	* Consumer:
	* Trigger RDMA write into RMBE of peer and send CDC, if RMBE space available.
	*
	* Copyright IBM Corp. 2016
	*
	* Author(s): Ursula Braun <ubraun@linux.vnet.ibm.com>
	*/

	#include <linux/net.h>
	#include <linux/rcupdate.h>
	#include <linux/workqueue.h>
	#include <linux/sched/signal.h>

	#include <net/sock.h>
	#include <net/tcp.h>

	#include "smc.h"
	#include "smc_wr.h"
	#include "smc_cdc.h"
	#include "smc_close.h"
	#include "smc_ism.h"
	#include "smc_tx.h"

	#define SMC_TX_WORK_DELAY 0
	#define SMC_TX_CORK_DELAY (HZ >> 2) /* 250 ms */

	/*************************** sndbuf producer *****************************/

	/* callback implementation for sk.sk_write_space()
	* to wakeup sndbuf producers that blocked with smc_tx_wait().
	* called under sk_socket lock.
	*/
	static void smc_tx_write_space(struct sock *sk)
	{
	struct socket *sock = sk->sk_socket;
	struct smc_sock *smc = smc_sk(sk);
	struct socket_wq *wq;

	/* similar to sk_stream_write_space */
	if (atomic_read(&smc->conn.sndbuf_space) && sock) {
	clear_bit(SOCK_NOSPACE, &sock->flags);
	rcu_read_lock();
	wq = rcu_dereference(sk->sk_wq);
	if (skwq_has_sleeper(wq))
	wake_up_interruptible_poll(&wq->wait,
	EPOLLOUT \| EPOLLWRNORM \|
	EPOLLWRBAND);
	if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
	sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
	rcu_read_unlock();
	}
	}

	/* Wakeup sndbuf producers that blocked with smc_tx_wait().
	* Cf. tcp_data_snd_check()=>tcp_check_space()=>tcp_new_space().
	*/
	void smc_tx_sndbuf_nonfull(struct smc_sock *smc)
	{
	if (smc->sk.sk_socket &&
	test_bit(SOCK_NOSPACE, &smc->sk.sk_socket->flags))
	smc->sk.sk_write_space(&smc->sk);
	}

	/* blocks sndbuf producer until at least one byte of free space available
	* or urgent Byte was consumed
	*/
	static int smc_tx_wait(struct smc_sock *smc, int flags)
	{
	DEFINE_WAIT_FUNC(wait, woken_wake_function);
	struct smc_connection *conn = &smc->conn;
	struct sock *sk = &smc->sk;
	long timeo;
	int rc = 0;

	/* similar to sk_stream_wait_memory */
	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
	add_wait_queue(sk_sleep(sk), &wait);
	while (1) {
	sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
	if (sk->sk_err \|\|
	(sk->sk_shutdown & SEND_SHUTDOWN) \|\|
	conn->killed \|\|
	conn->local_tx_ctrl.conn_state_flags.peer_done_writing) {
	rc = -EPIPE;
	break;
	}
	if (smc_cdc_rxed_any_close(conn)) {
	rc = -ECONNRESET;
	break;
	}
	if (!timeo) {
	/* ensure EPOLLOUT is subsequently generated */
	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
	rc = -EAGAIN;
	break;
	}
	if (signal_pending(current)) {
	rc = sock_intr_errno(timeo);
	break;
	}
	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
	if (atomic_read(&conn->sndbuf_space) && !conn->urg_tx_pend)
	break; /* at least 1 byte of free & no urgent data */
	set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
	sk_wait_event(sk, &timeo,
	sk->sk_err \|\|
	(sk->sk_shutdown & SEND_SHUTDOWN) \|\|
	smc_cdc_rxed_any_close(conn) \|\|
	(atomic_read(&conn->sndbuf_space) &&
	!conn->urg_tx_pend),
	&wait);
	}
	remove_wait_queue(sk_sleep(sk), &wait);
	return rc;
	}

	static bool smc_tx_is_corked(struct smc_sock *smc)
	{
	struct tcp_sock *tp = tcp_sk(smc->clcsock->sk);

	return (tp->nonagle & TCP_NAGLE_CORK) ? true : false;
	}

	/* sndbuf producer: main API called by socket layer.
	* called under sock lock.
	*/
	int smc_tx_sendmsg(struct smc_sock smc, struct msghdr msg, size_t len)
	{
	size_t copylen, send_done = 0, send_remaining = len;
	size_t chunk_len, chunk_off, chunk_len_sum;
	struct smc_connection *conn = &smc->conn;
	union smc_host_cursor prep;
	struct sock *sk = &smc->sk;
	char *sndbuf_base;
	int tx_cnt_prep;
	int writespace;
	int rc, chunk;

	/* This should be in poll */
	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);

	if (sk->sk_err \|\| (sk->sk_shutdown & SEND_SHUTDOWN)) {
	rc = -EPIPE;
	goto out_err;
	}

	while (msg_data_left(msg)) {
	if (sk->sk_state == SMC_INIT)
	return -ENOTCONN;
	if (smc->sk.sk_shutdown & SEND_SHUTDOWN \|\|
	(smc->sk.sk_err == ECONNABORTED) \|\|
	conn->killed)
	return -EPIPE;
	if (smc_cdc_rxed_any_close(conn))
	return send_done ?: -ECONNRESET;

	if (msg->msg_flags & MSG_OOB)
	conn->local_tx_ctrl.prod_flags.urg_data_pending = 1;

	if (!atomic_read(&conn->sndbuf_space) \|\| conn->urg_tx_pend) {
	if (send_done)
	return send_done;
	rc = smc_tx_wait(smc, msg->msg_flags);
	if (rc)
	goto out_err;
	continue;
	}

	/* initialize variables for 1st iteration of subsequent loop */
	/* could be just 1 byte, even after smc_tx_wait above */
	writespace = atomic_read(&conn->sndbuf_space);
	/* not more than what user space asked for */
	copylen = min_t(size_t, send_remaining, writespace);
	/* determine start of sndbuf */
	sndbuf_base = conn->sndbuf_desc->cpu_addr;
	smc_curs_copy(&prep, &conn->tx_curs_prep, conn);
	tx_cnt_prep = prep.count;
	/* determine chunks where to write into sndbuf */
	/* either unwrapped case, or 1st chunk of wrapped case */
	chunk_len = min_t(size_t, copylen, conn->sndbuf_desc->len -
	tx_cnt_prep);
	chunk_len_sum = chunk_len;
	chunk_off = tx_cnt_prep;
	smc_sndbuf_sync_sg_for_cpu(conn);
	for (chunk = 0; chunk < 2; chunk++) {
	rc = memcpy_from_msg(sndbuf_base + chunk_off,
	msg, chunk_len);
	if (rc) {
	smc_sndbuf_sync_sg_for_device(conn);
	if (send_done)
	return send_done;
	goto out_err;
	}
	send_done += chunk_len;
	send_remaining -= chunk_len;

	if (chunk_len_sum == copylen)
	break; /* either on 1st or 2nd iteration */
	/* prepare next (== 2nd) iteration */
	chunk_len = copylen - chunk_len; /* remainder */
	chunk_len_sum += chunk_len;
	chunk_off = 0; /* modulo offset in send ring buffer */
	}
	smc_sndbuf_sync_sg_for_device(conn);
	/* update cursors */
	smc_curs_add(conn->sndbuf_desc->len, &prep, copylen);
	smc_curs_copy(&conn->tx_curs_prep, &prep, conn);
	/* increased in send tasklet smc_cdc_tx_handler() */
	smp_mb__before_atomic();
	atomic_sub(copylen, &conn->sndbuf_space);
	/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
	smp_mb__after_atomic();
	/* since we just produced more new data into sndbuf,
	* trigger sndbuf consumer: RDMA write into peer RMBE and CDC
	*/
	if ((msg->msg_flags & MSG_OOB) && !send_remaining)
	conn->urg_tx_pend = true;
	if ((msg->msg_flags & MSG_MORE \|\| smc_tx_is_corked(smc)) &&
	(atomic_read(&conn->sndbuf_space) >
	(conn->sndbuf_desc->len >> 1)))
	/* for a corked socket defer the RDMA writes if there
	* is still sufficient sndbuf_space available
	*/
	queue_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
	SMC_TX_CORK_DELAY);
	else
	smc_tx_sndbuf_nonempty(conn);
	} /* while (msg_data_left(msg)) */

	return send_done;

	out_err:
	rc = sk_stream_error(sk, msg->msg_flags, rc);
	/* make sure we wake any epoll edge trigger waiter */
	if (unlikely(rc == -EAGAIN))
	sk->sk_write_space(sk);
	return rc;
	}

	/*************************** sndbuf consumer *****************************/

	/* sndbuf consumer: actual data transfer of one target chunk with ISM write */
	int smcd_tx_ism_write(struct smc_connection conn, void data, size_t len,
	u32 offset, int signal)
	{
	struct smc_ism_position pos;
	int rc;

	memset(&pos, 0, sizeof(pos));
	pos.token = conn->peer_token;
	pos.index = conn->peer_rmbe_idx;
	pos.offset = conn->tx_off + offset;
	pos.signal = signal;
	rc = smc_ism_write(conn->lgr->smcd, &pos, data, len);
	if (rc)
	conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
	return rc;
	}

	/* sndbuf consumer: actual data transfer of one target chunk with RDMA write */
	static int smc_tx_rdma_write(struct smc_connection *conn, int peer_rmbe_offset,
	int num_sges, struct ib_rdma_wr *rdma_wr)
	{
	struct smc_link_group *lgr = conn->lgr;
	struct smc_link *link = conn->lnk;
	int rc;

	rdma_wr->wr.wr_id = smc_wr_tx_get_next_wr_id(link);
	rdma_wr->wr.num_sge = num_sges;
	rdma_wr->remote_addr =
	lgr->rtokens[conn->rtoken_idx][link->link_idx].dma_addr +
	/* RMBE within RMB */
	conn->tx_off +
	/* offset within RMBE */
	peer_rmbe_offset;
	rdma_wr->rkey = lgr->rtokens[conn->rtoken_idx][link->link_idx].rkey;
	rc = ib_post_send(link->roce_qp, &rdma_wr->wr, NULL);
	if (rc)
	smcr_link_down_cond_sched(link);
	return rc;
	}

	/* sndbuf consumer */
	static inline void smc_tx_advance_cursors(struct smc_connection *conn,
	union smc_host_cursor *prod,
	union smc_host_cursor *sent,
	size_t len)
	{
	smc_curs_add(conn->peer_rmbe_size, prod, len);
	/* increased in recv tasklet smc_cdc_msg_rcv() */
	smp_mb__before_atomic();
	/* data in flight reduces usable snd_wnd */
	atomic_sub(len, &conn->peer_rmbe_space);
	/* guarantee 0 <= peer_rmbe_space <= peer_rmbe_size */
	smp_mb__after_atomic();
	smc_curs_add(conn->sndbuf_desc->len, sent, len);
	}

	/* SMC-R helper for smc_tx_rdma_writes() */
	static int smcr_tx_rdma_writes(struct smc_connection *conn, size_t len,
	size_t src_off, size_t src_len,
	size_t dst_off, size_t dst_len,
	struct smc_rdma_wr *wr_rdma_buf)
	{
	struct smc_link *link = conn->lnk;

	dma_addr_t dma_addr =
	sg_dma_address(conn->sndbuf_desc->sgt[link->link_idx].sgl);
	int src_len_sum = src_len, dst_len_sum = dst_len;
	int sent_count = src_off;
	int srcchunk, dstchunk;
	int num_sges;
	int rc;

	for (dstchunk = 0; dstchunk < 2; dstchunk++) {
	struct ib_sge *sge =
	wr_rdma_buf->wr_tx_rdma[dstchunk].wr.sg_list;

	num_sges = 0;
	for (srcchunk = 0; srcchunk < 2; srcchunk++) {
	sge[srcchunk].addr = dma_addr + src_off;
	sge[srcchunk].length = src_len;
	num_sges++;

	src_off += src_len;
	if (src_off >= conn->sndbuf_desc->len)
	src_off -= conn->sndbuf_desc->len;
	/* modulo in send ring */
	if (src_len_sum == dst_len)
	break; /* either on 1st or 2nd iteration */
	/* prepare next (== 2nd) iteration */
	src_len = dst_len - src_len; /* remainder */
	src_len_sum += src_len;
	}
	rc = smc_tx_rdma_write(conn, dst_off, num_sges,
	&wr_rdma_buf->wr_tx_rdma[dstchunk]);
	if (rc)
	return rc;
	if (dst_len_sum == len)
	break; /* either on 1st or 2nd iteration */
	/* prepare next (== 2nd) iteration */
	dst_off = 0; /* modulo offset in RMBE ring buffer */
	dst_len = len - dst_len; /* remainder */
	dst_len_sum += dst_len;
	src_len = min_t(int, dst_len, conn->sndbuf_desc->len -
	sent_count);
	src_len_sum = src_len;
	}
	return 0;
	}

	/* SMC-D helper for smc_tx_rdma_writes() */
	static int smcd_tx_rdma_writes(struct smc_connection *conn, size_t len,
	size_t src_off, size_t src_len,
	size_t dst_off, size_t dst_len)
	{
	int src_len_sum = src_len, dst_len_sum = dst_len;
	int srcchunk, dstchunk;
	int rc;

	for (dstchunk = 0; dstchunk < 2; dstchunk++) {
	for (srcchunk = 0; srcchunk < 2; srcchunk++) {
	void *data = conn->sndbuf_desc->cpu_addr + src_off;

	rc = smcd_tx_ism_write(conn, data, src_len, dst_off +
	sizeof(struct smcd_cdc_msg), 0);
	if (rc)
	return rc;
	dst_off += src_len;
	src_off += src_len;
	if (src_off >= conn->sndbuf_desc->len)
	src_off -= conn->sndbuf_desc->len;
	/* modulo in send ring */
	if (src_len_sum == dst_len)
	break; /* either on 1st or 2nd iteration */
	/* prepare next (== 2nd) iteration */
	src_len = dst_len - src_len; /* remainder */
	src_len_sum += src_len;
	}
	if (dst_len_sum == len)
	break; /* either on 1st or 2nd iteration */
	/* prepare next (== 2nd) iteration */
	dst_off = 0; /* modulo offset in RMBE ring buffer */
	dst_len = len - dst_len; /* remainder */
	dst_len_sum += dst_len;
	src_len = min_t(int, dst_len, conn->sndbuf_desc->len - src_off);
	src_len_sum = src_len;
	}
	return 0;
	}

	/* sndbuf consumer: prepare all necessary (src&dst) chunks of data transmit;
	* usable snd_wnd as max transmit
	*/
	static int smc_tx_rdma_writes(struct smc_connection *conn,
	struct smc_rdma_wr *wr_rdma_buf)
	{
	size_t len, src_len, dst_off, dst_len; /* current chunk values */
	union smc_host_cursor sent, prep, prod, cons;
	struct smc_cdc_producer_flags *pflags;
	int to_send, rmbespace;
	int rc;

	/* source: sndbuf */
	smc_curs_copy(&sent, &conn->tx_curs_sent, conn);
	smc_curs_copy(&prep, &conn->tx_curs_prep, conn);
	/* cf. wmem_alloc - (snd_max - snd_una) */
	to_send = smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep);
	if (to_send <= 0)
	return 0;

	/* destination: RMBE */
	/* cf. snd_wnd */
	rmbespace = atomic_read(&conn->peer_rmbe_space);
	if (rmbespace <= 0)
	return 0;
	smc_curs_copy(&prod, &conn->local_tx_ctrl.prod, conn);
	smc_curs_copy(&cons, &conn->local_rx_ctrl.cons, conn);

	/* if usable snd_wnd closes ask peer to advertise once it opens again */
	pflags = &conn->local_tx_ctrl.prod_flags;
	pflags->write_blocked = (to_send >= rmbespace);
	/* cf. usable snd_wnd */
	len = min(to_send, rmbespace);

	/* initialize variables for first iteration of subsequent nested loop */
	dst_off = prod.count;
	if (prod.wrap == cons.wrap) {
	/* the filled destination area is unwrapped,
	* hence the available free destination space is wrapped
	* and we need 2 destination chunks of sum len; start with 1st
	* which is limited by what's available in sndbuf
	*/
	dst_len = min_t(size_t,
	conn->peer_rmbe_size - prod.count, len);
	} else {
	/* the filled destination area is wrapped,
	* hence the available free destination space is unwrapped
	* and we need a single destination chunk of entire len
	*/
	dst_len = len;
	}
	/* dst_len determines the maximum src_len */
	if (sent.count + dst_len <= conn->sndbuf_desc->len) {
	/* unwrapped src case: single chunk of entire dst_len */
	src_len = dst_len;
	} else {
	/* wrapped src case: 2 chunks of sum dst_len; start with 1st: */
	src_len = conn->sndbuf_desc->len - sent.count;
	}

	if (conn->lgr->is_smcd)
	rc = smcd_tx_rdma_writes(conn, len, sent.count, src_len,
	dst_off, dst_len);
	else
	rc = smcr_tx_rdma_writes(conn, len, sent.count, src_len,
	dst_off, dst_len, wr_rdma_buf);
	if (rc)
	return rc;

	if (conn->urg_tx_pend && len == to_send)
	pflags->urg_data_present = 1;
	smc_tx_advance_cursors(conn, &prod, &sent, len);
	/* update connection's cursors with advanced local cursors */
	smc_curs_copy(&conn->local_tx_ctrl.prod, &prod, conn);
	/* dst: peer RMBE */
	smc_curs_copy(&conn->tx_curs_sent, &sent, conn);/* src: local sndbuf */

	return 0;
	}

	/* Wakeup sndbuf consumers from any context (IRQ or process)
	* since there is more data to transmit; usable snd_wnd as max transmit
	*/
	static int smcr_tx_sndbuf_nonempty(struct smc_connection *conn)
	{
	struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
	struct smc_link *link = conn->lnk;
	struct smc_rdma_wr *wr_rdma_buf;
	struct smc_cdc_tx_pend *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	if (!link \|\| !smc_wr_tx_link_hold(link))
	return -ENOLINK;
	rc = smc_cdc_get_free_slot(conn, link, &wr_buf, &wr_rdma_buf, &pend);
	if (rc < 0) {
	smc_wr_tx_link_put(link);
	if (rc == -EBUSY) {
	struct smc_sock *smc =
	container_of(conn, struct smc_sock, conn);

	if (smc->sk.sk_err == ECONNABORTED)
	return sock_error(&smc->sk);
	if (conn->killed)
	return -EPIPE;
	rc = 0;
	mod_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
	SMC_TX_WORK_DELAY);
	}
	return rc;
	}

	spin_lock_bh(&conn->send_lock);
	if (link != conn->lnk) {
	/* link of connection changed, tx_work will restart */
	smc_wr_tx_put_slot(link,
	(struct smc_wr_tx_pend_priv *)pend);
	rc = -ENOLINK;
	goto out_unlock;
	}
	if (!pflags->urg_data_present) {
	rc = smc_tx_rdma_writes(conn, wr_rdma_buf);
	if (rc) {
	smc_wr_tx_put_slot(link,
	(struct smc_wr_tx_pend_priv *)pend);
	goto out_unlock;
	}
	}

	rc = smc_cdc_msg_send(conn, wr_buf, pend);
	if (!rc && pflags->urg_data_present) {
	pflags->urg_data_pending = 0;
	pflags->urg_data_present = 0;
	}

	out_unlock:
	spin_unlock_bh(&conn->send_lock);
	smc_wr_tx_link_put(link);
	return rc;
	}

	static int smcd_tx_sndbuf_nonempty(struct smc_connection *conn)
	{
	struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
	int rc = 0;

	spin_lock_bh(&conn->send_lock);
	if (!pflags->urg_data_present)
	rc = smc_tx_rdma_writes(conn, NULL);
	if (!rc)
	rc = smcd_cdc_msg_send(conn);

	if (!rc && pflags->urg_data_present) {
	pflags->urg_data_pending = 0;
	pflags->urg_data_present = 0;
	}
	spin_unlock_bh(&conn->send_lock);
	return rc;
	}

	int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
	{
	int rc;

	if (conn->killed \|\|
	conn->local_rx_ctrl.conn_state_flags.peer_conn_abort)
	return -EPIPE; /* connection being aborted */
	if (conn->lgr->is_smcd)
	rc = smcd_tx_sndbuf_nonempty(conn);
	else
	rc = smcr_tx_sndbuf_nonempty(conn);

	if (!rc) {
	/* trigger socket release if connection is closing */
	struct smc_sock *smc = container_of(conn, struct smc_sock,
	conn);
	smc_close_wake_tx_prepared(smc);
	}
	return rc;
	}

	/* Wakeup sndbuf consumers from process context
	* since there is more data to transmit
	*/
	void smc_tx_work(struct work_struct *work)
	{
	struct smc_connection *conn = container_of(to_delayed_work(work),
	struct smc_connection,
	tx_work);
	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
	int rc;

	lock_sock(&smc->sk);
	if (smc->sk.sk_err)
	goto out;

	rc = smc_tx_sndbuf_nonempty(conn);
	if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked &&
	!atomic_read(&conn->bytes_to_rcv))
	conn->local_rx_ctrl.prod_flags.write_blocked = 0;

	out:
	release_sock(&smc->sk);
	}

	void smc_tx_consumer_update(struct smc_connection *conn, bool force)
	{
	union smc_host_cursor cfed, cons, prod;
	int sender_free = conn->rmb_desc->len;
	int to_confirm;

	smc_curs_copy(&cons, &conn->local_tx_ctrl.cons, conn);
	smc_curs_copy(&cfed, &conn->rx_curs_confirmed, conn);
	to_confirm = smc_curs_diff(conn->rmb_desc->len, &cfed, &cons);
	if (to_confirm > conn->rmbe_update_limit) {
	smc_curs_copy(&prod, &conn->local_rx_ctrl.prod, conn);
	sender_free = conn->rmb_desc->len -
	smc_curs_diff_large(conn->rmb_desc->len,
	&cfed, &prod);
	}

	if (conn->local_rx_ctrl.prod_flags.cons_curs_upd_req \|\|
	force \|\|
	((to_confirm > conn->rmbe_update_limit) &&
	((sender_free <= (conn->rmb_desc->len / 2)) \|\|
	conn->local_rx_ctrl.prod_flags.write_blocked))) {
	if (conn->killed \|\|
	conn->local_rx_ctrl.conn_state_flags.peer_conn_abort)
	return;
	if ((smc_cdc_get_slot_and_msg_send(conn) < 0) &&
	!conn->killed) {
	queue_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
	SMC_TX_WORK_DELAY);
	return;
	}
	}
	if (conn->local_rx_ctrl.prod_flags.write_blocked &&
	!atomic_read(&conn->bytes_to_rcv))
	conn->local_rx_ctrl.prod_flags.write_blocked = 0;
	}

	/*************************** send initialize *****************************/

	/* Initialize send properties on connection establishment. NB: not __init! */
	void smc_tx_init(struct smc_sock *smc)
	{
	smc->sk.sk_write_space = smc_tx_write_space;
	}